From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx109.postini.com [74.125.245.109]) by kanga.kvack.org (Postfix) with SMTP id BD87E6B0071 for ; Thu, 25 Oct 2012 05:24:27 -0400 (EDT) Date: Thu, 25 Oct 2012 11:24:24 +0200 From: Borislav Petkov Subject: Re: [PATCH] add some drop_caches documentation and info messsge Message-ID: <20121025092424.GA16601@liondog.tnic> References: <20121023164546.747e90f6.akpm@linux-foundation.org> <20121024062938.GA6119@dhcp22.suse.cz> <20121024125439.c17a510e.akpm@linux-foundation.org> <50884F63.8030606@linux.vnet.ibm.com> <20121024134836.a28d223a.akpm@linux-foundation.org> <20121024210600.GA17037@liondog.tnic> <50885B2E.5050500@linux.vnet.ibm.com> <20121024224817.GB8828@liondog.tnic> <5088725B.2090700@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: KOSAKI Motohiro Cc: Dave Hansen , Andrew Morton , Michal Hocko , linux-mm@kvack.org, KAMEZAWA Hiroyuki , LKML On Wed, Oct 24, 2012 at 08:56:45PM -0400, KOSAKI Motohiro wrote: > > That effectively means removing it from the kernel since distros ship > > with those config options off. We don't want to do that since there > > _are_ valid, occasional uses like benchmarking that we want to be > > consistent. > > Agreed. we don't want to remove valid interface never. Ok, duly noted. But let's discuss this a bit further. So, for the benchmarking aspect, you're either going to have to always require dmesg along with benchmarking results or /proc/vmstat, depending on where the drop_caches stats end up. Is this how you envision it? And then there are the VM bug cases, where you might not always get full dmesg from a panicked system. In that case, you'd want the kernel tainting thing too, so that it at least appears in the oops backtrace. Although the tainting thing might not be enough - a user could drop_caches at some point in time and the oops happening much later could be unrelated but that can't be expressed in taint flags. So you'd need some sort of a drop_caches counter, I'd guess. Or a last drop_caches timestamp something. Am I understanding the intent correctly? Thanks. -- Regards/Gruss, Boris. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org